and tied to seismic data. Projections of the in-situ measurements on seismic profiles have shown that the study area not only accommodates zones of shallow and dense GH; but also zones where solid hydrate and free gas coexist as well as pockets of free gas. Further analysis of several seismic profiles has allowed illustrating the detailed GH occurrence zone within the study area, estimate its volume and its occupancy ratio of the pockmark. Correlations between GH content and 3D bathymetry sections have allowed to draw a link between different GH contents and the morphology of the pockmark, which also shares similarities with the morphology of the GH occurrence zone it accommodates.

Tan, J., Sephton, M.A., 2019. Organic records of early life on Mars: The role of iron, burial, and kinetics on preservation. Astrobiology 20, 53-72.

https://doi.org/10.1089/ast.2019.2046 Samples that are likely to contain evidence of past life on Mars must have been deposited when and where environments exhibited habitable conditions. Mars analog sites provide the opportunity to study how life could have exploited such habitable conditions. Acidic iron- and sulfur-rich streams are good geochemical analogues for the late Noachian and early Hesperian, periods of martian history where habitable conditions were widespread. Past life on Mars would have left behind fossilized microbial organic remains. These are often- sought diagnostic evidence, but they must be shielded from the harsh radiation flux at the martian surface and its deleterious effect on organic matter. One mechanism that promotes such preservation is burial, which raises questions about how organic biomarkers are influenced by the postburial effects of diagenesis. We investigated the kinetics of organic degradation in the subsurface of Mars. Natural mixtures of acidic iron- and sulfur-rich stream sediments and their associated microbial populations and remains were subjected to hydrous pyrolysis, which simulated the increased temperatures and pressures of burial alongside any promoted organic/mineral interactions. Calculations were made to extrapolate the observed changes over martian history. Our experiments indicate that low carbon contents, high water-to-rock ratios, and the presence of iron-rich minerals combine to provide unfavorable conditions for the preservation of soluble organic matter over the billions of years necessary to produce present-day organic records of late Noachian and early Hesperian life on Mars. Successful sample selection strategies must therefore consider the pre-, syn-, and postburial histories of sedimentary records on Mars and the balance between the production of biomass and the long-term preservation of organic biomarkers over geological time.

Tan, N., Contoux, C., Ramstein, G., Sun, Y., Dumas, C., Sepulchre, P., Guo, Z., 2020. Modeling a modern-like p CO warm period (Marine Isotope Stage KM5c) with two versions of an Institut Pierre Simon Laplace 2 atmosphere - ocean coupled general circulation model. Climate of the Past 16, 1-16.

https://www.clim-past.net/16/1/2020/ The mid- Piacenzian warm period (3.264 to 3.025 Ma) is the most recent geological period with present -like p atmospheric CO and is thus expected to have exhibited a warm climate similar to or warmer than the present 2 day. On the basis of understanding that has been gathered on the climate variability of this interval, a specific interglacial (Marine Isotope Stage KM5c, MIS KM5c ; 3.205 Ma) has been selected for the Pliocene Model Intercomparison Project phase 2 (PlioMIP 2). We carried out a series of experiments according to the design of PlioMIP2 with two versions of the Institut Pierre Simon Laplace (IPSL) atmosphere - ocean coupled general circulation model (AOGCM): IPSL-CM5A and IPSL-CM5A2. Compared to the PlioMIP 1 experiment, run with IPSL-CM5A, our results show that the simulated MIS KM5c climate presents enhanced warming in mid- to high latitudes, especially over oceanic regions. This warming can be largely attributed to the enhanced Atlantic Meridional Overturning Circulation caused by the high-latitude seaway changes. The sensitivity p experiments, conducted with IPSL-CM5A2, show that besides the increased CO , both modified orography 2 and reduced ice sheets contribute substantially to mid- to high latitude warming in MIS KM5c. When p considering the CO uncertainties (+/- 50 ppmv) during the Pliocene, the response of the modeled mean 2 p annual surface air temperature to changes to CO (+/-50 ppmv) is not symmetric, which is likely due to the 2 nonlinear response of the cryosphere (snow cover and sea ice extent). By analyzing the Greenland Ice Sheet surface mass balance, we also demonstrate its vulnerability under both MIS KM5c and modern warm climate.